There have been many predictions and theories regarding the storyline of DC's upcoming Elseworlds project, Joker: Folie à Deux. After the massive success of 2019's Joker, director Todd Phillips is returning to expand his franchise separate to the main DC Universe continuity. Joker: Folie à Deux is expected to release on October 4, 2024, and will see the return of Joaquin Phoenix as Arthur Fleck, a struggling stand-up comedian whose descent into mental illness and nihilism saw him become the Joker and spark a revolution against the wealthy elite of Gotham City. Adapted from the iconic DC Comics villain, the Joker's story will continue in Joker: Folie à Deux.

While Joker was planned as a standalone story exploring a new, more realistic, origin story for the DC villain, Phillips confirmed the development of a sequel in June 2022, and announced the film's title to be Joker: Folie à Deux. Lady Gaga was cast as Harley Quinn, the Joker's love-interest and partner-in-crime in DC Comics, while Zazie Beetz is returning as Sophie Dumond, and Brendan Gleeson, Catherine Keener, Jacob Lofland, and Harry Lawtey have also joined the cast of Joker: Folie à Deux. Since the film's confirmation, many theories and predictions have been posed concerning Joker: Folie à Deux's storyline, which suggest an exciting addition to Phillips' DC Elseworlds franchise.

10 Arthur Fleck Inspires The Rise Of The Actual Joker

Prior to Lady Gaga's casting in Joker: Folie à Deux, many attributed the title (which translates to "Madness for Two") to the idea that copycats could present themselves after Arthur Fleck's actions in Joker started a revolution. While it now seems that the madness will be shared between Arthur Fleck and Harley Quinn, it's still possible that Joker: Folie à Deux could feature more than one Joker. A video from the set of Joker: Folie à Deux (via Twitter) revealed Fleck being chased by other characters sporting Joker outfits, and if these aren't copycats, it's possible that Arthur Fleck could have inspired the real Joker to start his crime spree.

9 Harvey Dent Will Become Two-Face In Joker 2

In set photos from Joker: Folie à Deux (via Twitter) released in March 2023, banners can be seen sporting slogans such as "Dent is a Clown." This all but confirms that DC Comics' Harvey Dent will be making his debut in the Joker sequel, after previously being portrayed by the likes of Tommy Lee Jones, Aaron Eckhart, and Misha Collins. Dent was once the District Attorney of Gotham City, but became the villain known as Two-Face after being attacked with acidic chemicals during a court trial. As the DA, Dent could be a great rival to Fleck and Quinn, and could potentially even become Two-Face in Joker: Folie à Deux.

8 Joaquin Phoenix May Break An Oscars Record

Joker set some huge records after its 2019, including becoming the first R-rated film to pass $1 billion, becoming the sixth-highest grossing film of 2019, and earning many accolades during awards season. The bulk of Joker's awards were won by Hildur Guðnadóttir for the film's score, and Joaquin Phoenix for portraying Arthur Fleck, and these included the Oscars in their respective categories at 2020's 92nd Academy Awards. Joker: Folie à Deux could make Academy Awards history, as Joaquin Phoenix would be the first actor to receive two Oscars for portraying the same character in different films, and it's entirely possible given the impact of his initial performance in Joker.

7 Joker 2 Could Include Batman

In DC Comics, the Joker and Batman are intrinsically linked, and this translated in part into a minor storyline in 2019's Joker. A young Bruce Wayne was seen, while the film also explored Batman's memorable origin story as his parents were killed by a member of the Joker's mob. This ending makes it difficult for Joker: Folie à Deux to ignore Batman and his vengeful quest against the Joker. There is speculation that a time-jump could age up Bruce Wayne, and Arthur Fleck's unreliable narration in Joker poses some opportunities for the timeline to be changed, so it's possible that a new Batman could debut in Joker: Folie à Deux.

6 Brendan Gleeson Is Playing Commissioner Gordon In Joker 2

By the ending of Joker, Arthur Fleck had become a highly-publicized criminal who murdered Robert De Niro's Murray Franklin on live TV and incited huge riots across Gotham City. This would surely garner the attention of Gotham City's Police Department, led by Commissioner Jim Gordon, a legendary ally to Batman in DC Comics. Harry Potter and The Banshees of Inisherin's Brendan Gleeson joined the cast of Joker: Folie à Deux in September 2022, and many expected him to be portraying Commissioner Gordon. Previously portrayed by the likes of J. K. Simmons and Gary Oldman, Commissioner Gordon would be the perfect character for Brendan Gleeson in Joker: Folie à Deux.

5 Joker 2 Will Be The First R Rated Musical To Make $1 Billion

Joker surprised many in 2019 by grossing over $1 billion throughout its theatrical run, marking a major profit for Warner Bros. as it was made on a budget of only $70 million (approximately). Though audiences' perspectives of comic book movie adaptations may have changed since then - with the turmoil at Warner Bros. and DC Studios, and superhero fatigue and quality issues plaguing Marvel Studios' MCU - it's possible that Joker: Folie à Deux could follow the success of its predecessor. With its confirmed musical themes, Joker: Folie à Deux making over $1 billion would make it the first R-rated musical in history to achieve such financial success.

4 Arthur Fleck Could Tell A Different Origin Story In Joker 2

While the consensus suggests that not all of Joker's story was actually real, as Arthur Fleck was an incredibly unreliable narrator, one theory posed by Reddit user italyprayer suggests that the entire film could have been a fabricated story. The theory cites Todd Phillips in the featurette Joker: Vision & Fury, who states, "[Arthur] might not be the Joker... This is just a version of a Joker origin. It's just the version this guy is telling." This means that Joker: Folie à Deux could rewind time and tell a completely different origin story for the Joker, hammering home the idea that Arthur's version of events may not be trustworthy.

3 Joker 2 Will Introduce Arthur Fleck's Son

Though the title Joker: Folie à Deux could refer to delusions shared by Arthur Fleck with either Harley Quinn or various other Jokers, one theory posed by Reddit user MySockHurts suggests that Arthur Fleck's son could be introduced in the upcoming film. This would perhaps be possible should a time-jump occur in Folie à Deux, as he could debut as the child of Arthur and Harley Quinn. This theory arose as Folie à Deux often arises between two members of the same family, so it would make sense for a member of Arthur Fleck's family to debut, and perhaps it will be his son who becomes the true Joker.

2 Harley Quinn Is A Figment Of Arthur Fleck's Imagination

Lady Gaga's casting as Harley Quinn in Joker: Folie à Deux was very exciting for avid DC fans, as the pair make a fantastically evil partnership in many iconic DC Comics. Originally a psychiatrist named Dr. Harleen Quinzel, she later becomes the Joker's accomplice and renames herself Harley Quinn. With Folie à Deux's Arkham Asylum setting, it's possible this origin story could be told, but one theory suggests that Harley Quinn doesn't actually exist, but is the side of Quinzel that Arthur sees in his delusions. A similar pattern unfolded involving his relationship with Sophie in Joker, so this would be a great way to subvert expectations in Folie à Deux.

1 Joker 2 Will Be DC's Version Of One Flew Over The Cuckoo's Nest

Joker: Folie à Deux taking place within Arkham Asylum has led many to draw comparisons between Arkham and the Oregon State Hospital in Miloš Forman's One Flew Over the Cuckoo's Nest. During the 1975 film, Jack Nicholson's Randle McMurphy unsuccessfully makes several attempts to escape from the mental institution, thwarted along the way by the sinister Mildred Ratched. Reddit user DarthVaderIsMyWaifu suggests Joker: Folie à Deux could adapt a similar storyline, as Arthur Fleck and Harley Quinn could make several attempts to escape from Arkham Asylum, perhaps with the help of other patients, though it's unclear if Arthur would be as unsuccessful as Nicholson's ill-fated character.